The use of endovascular techniques for the implantation of medical devices for the treatment and the occlusion of body cavities such as arteries, veins, fallopian tubes or vascular deformities is known in the art. For example, occlusion of vascular aneurysms can be performed using an implantable device, such as an intrasaccular implant, that is introduced with the aid of an endovascular delivery wire through a catheter. Once moved to the treatment site, the intrasaccular implant can be moved into the aneurysm cavity to occlude the aneurysm.
The severance of the implant from the delivery wire can be problematic. On the one hand, the device must be capable of forming a small profile as possible to be guided through the fine bore of the catheter to its destination, while on the other hand it must bring about a reliable severance of the implant. Absent a reliable severance of the intrasaccular implant, withdrawal of the delivery wire and catheter may cause unintended removal of the intrasaccular implant from the cavity to be occluded and thus injure and/or rupture of the wall of the cavity or vessel.
Traditional mechanical methods for the severance of implants from the insertion means are reliable. However, the necessary rigidity of the connection between the implant and the delivery means can impede the introduction of the implant. Furthermore, the low load carrying capacity of the connection due to its rigidity entails an appreciable risk of premature detachment of the insertion means from the occluding implant. Moreover, in the case of mechanical separation of the inserting wire and the implant, mechanical energy must be transmitted (e.g., by rotation of the inserting wire), which may cause the implant to be dislodged out of the correct position.
Traditional electrolytic severance of the implant involves using an electrolytically corrodible design on the end of the delivery wire at the connection between the delivery wire and the implant. Such a device can elegantly makes use of the voltage applied to the implant serving as an anode for electrothrombosis. However, the connection of the implant to the delivery wire is limited by the requirements of the electrolytically corrodible region. For example, the only materials that can be utilized are those which have a sufficiently high degree of strength to enable reliable guidance of the implant? through the delivery wire. The selection of materials for forming the point of eventual electrolytic severance is consequently extremely limited.
In the case of traditional devices for the electrolytic severance of implants, the implant and the delivery wire are not produced integrally, but instead are produced mechanically connected to each other. This design has the inherent disadvantage that the delivery wire must be tapered toward its end in an involved grinding operation in order to ensure sufficient strength in the proximal zone of the delivery wire while facilitating electrolytic, corrosive severance of the wire at the distal part of the delivery wire connected to the implant. In order to ensure sufficient strength of the connection point, the corrodible zone of the end of the delivery wire must not have a diameter below a certain minimum value since it is subjected to a high flexural load. The corrodible wire end representing the connection point between the implant and the delivery wire can be consequently extremely rigid and require a relatively long time for electrolytic corrosive severance.